1. Field of the Invention
The present invention relates to a process for depositing electroless nickel on zinc die cast substrates and the products made from the process, and more particularly, to a process comprising a series of metal electroplating and electroless nickel plating steps to provide a plurality of different metal layers on the zinc die cast substrate and in a preferred embodiment to the use of antimony in one or more of the electroless nickel plating baths.
2. Description of Related Art
Zinc die castings are used to make a variety of industrial and consumer products because of their low cost and ease of fabrication. The zinc die castings however, are not aesthetically pleasing and/or do not have the properties required for most products such as corrosion resistance or wearability. Accordingly, most zinc die cast products have a finish coating depending on the particular application or decorative effect required.
Electroless nickel has been used extensively to plate zinc die cast parts with a finished coating because of its many desired properties such as brightness, corrosion resistance, wearability and the like. Electroless nickel is not typically used for the direct plating of the zinc die casting, however, because of bath contamination and lack of adhesion between the zinc die casting and the electroless layer resulting in blistering and peeling of the electroless nickel layer. Processes have been developed to electrolessly nickel plate zinc die castings and one process utilizes an electrolytic copper strike coating on the zinc die casting followed by electroless nickel plating to produce the final coating. The electrolytic copper layer provides an adhesive coating for the electroless nickel layer and is likewise adhesive to the zinc die casting.
The use of electrolytic copper in industry is being sharply curtailed, however, because commercial electrolytic copper baths utilize cyanides which are toxic and environmentally undesirable. Additionally, the use of barrel plating is becoming more important then rack plating for many applications and new electroless nickel plating processes for zinc die castings must be versatile and useful for all types of plating processes including barrel plating, rack plating and immersion processes.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a process for plating zinc die castings with electroless nickel. It is a further object of the present invention to provide a process for plating zinc die castings with electroless nickel using any electroless nickel plating process such as rack, barrel and immersion plating processes.
Another object is to produce electrolessly nickel plated zinc die casting products.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.